While installing a conventional lamp, in addition to a bulb and a power cord, a lamp base and a shade must be also provided, which needs considerable space and wastes much time and labor for installation. Further, the lamp shades are often made of hard fragile material, which are easily damaged and deformed once being hit. For example, for installing a signal light on a car, a recess must be first formed on the car panel, a lamp base be secured to the recess, and a bulb is fixed on the base and then covered with a lamp shade fastened to the car panel or fender. Such installation process is cumbersome and takes much time and labor. Moreover, the lamp shade is extremely susceptible to breakage, even the bulb may be broken during car accidents.